Analysis of the protected inventions
Definition of terms
Although most of the terms employed throughout the disclosure are clear and correspond to the common usage of the terms in science, the term promoter ” naturally expressed” in plants is not expressly defined and, as such, leads to uncertainty about what promoters are covered by these claims. Does “naturally expressed” encompass only promoters from plant genes? or does it include promoters not found as part of plant genes but fully operable in plant cells? The following discussion provides a framework for approaching this issue.
What is a promoter “naturally expressed” in plants?
The inventors do not provide a precise definition for a promoter “naturally expressed in plants” in the disclosure. The file history of the United States patent 6174724, containing all the correspondence held between the U.S. Patent Office and the applicants during the examination process of the application until its issuance, does not reveal the exact scope of the concept either. However, a “guesstimate” of the concept can be drawn from the examples provided in the application and the statements made by the applicants and the examiner during the examination process.
During examination the patent application was initially rejected on the grounds of being enabling only for the use of the exemplified promoters from the nopaline synthase gene (nos) of the Agrobacterium Ti plasmid and from the ribulose−1,5−bis−phosphate carboxylase small subunit (rbcS) gene, a plant gene. At the time of the invention, 1983, identification, isolation and evaluation of promoters was not a routine task, and the examiner considered that the disclosure did not provide enough guidance for the use of any non−exemplified promoter expressed in plant cells. It appears that the examiner was envisioning promoters expressed in plants from any plant−expressed gene. Although the nos promoter is a promoter of bacterial origin, it was deemed to fall within the concept of plant−expressible promoters as it becomes operational only when the Agrobacterium T−DNA region integrates into the plant cell chromosome and commands the plant cell to initiate the transcription of the nos gene. The applicants finally overcame this ground of rejection by stating that full identification of the regulatory regions of a gene was not an absolute requirement for using the invention. They argued that they had provided a comprehensive method to evaluate the ability of non−exemplified promoters to drive the expression of an antibiotic resistance gene. Notably, the applicants did not disagree with the examiner’s “definition” of naturally expressed promoters.
A further useful insight on the meaning of the term can be gleaned from the applicants’ assertion that animal, yeast and bacterial−derived promoters are not plant−expressible promoters and therefore, are not expected to work in plants. They emphasized during the examination process that the promoter should be a plant−expressible promoter capable of functioning in a selected plant cell. The applicants made this assertion in light of experiments conducted by Herrera−Estrella et al. (Nature 303: 209−213, 1983) and Barton et al. (Cell32: 1033−1043, 1983) on promoters from plant origin and non−plant origin driving heterologous genes in plant cells 1. The exact quote by the applicants in the examination proceedings is as follows:
Therefore, a likely interpretation is that: